Apatite formation on titania-vaterite powders in simulated body fluid

Titania-hydroxyapatite composites were prepared by soaking compacts of a powder mixture consisting of crystalline titania and calcium carbonate (vaterite) to form apatite in simulated body fluid (SBF). The apatite crystal formed on compacts in SBF at 37 degreesC within 2 days. The apatite-forming ability of the mixtures was much higher than that of titania crystals such as anatase or rutile oil their own. Calcium carbonate (vaterite), which has high Solubility in the aqueous solution, plays an important role in the apatite formation; the dissolution is suggested to increase the supersaturation of the apatite in SBF. Formation of titanium hydroxide groups, which may induce the apatite formation, is drastically promoted on the powder-compacts by the soaking in SBF, independently of the structures of the titania crystals (anatase or rutile). The apatite formation on the compact of the titania-calcium carbonate (vaterite) powder mixture containing the anatase phase occurs in a shorter period than that oil the one of titania (rutile)-calcium carbonate (vaterite). Crystalline titania (anatase phase) is suggested to be particularly effective in inducing the apatite nucleation. (C) 2003 Elsevier Ltd. All rights reserved.